EVALUATION OF SOME MANAGEMENT STRATEGIES IN EUTROPHIC MOGAN LAKE, TURKEY: PHOSPHORUS MOBILITY IN THE SEDIMENT-WATER INTERFACE

Mogan Lake, a popular recreation area, is under the pressure of intense urban-industrial pollution, therefore some management strategies included occasional macrophyte harvesting, diverting running water into the lake to accelerate the improvement of its water, and dredging have been in progressing since 1995. This study was conducted on sediment and overlying water samples collected in April, July and October 2015 and January 2016 from Mogan Lake. The outstanding data for this study is presented as: i) detection of the sediment chemical composition and estimation of sediment phosphorus mobility, ii) comparison of the current status of the lake's eutrophication regarding phosphorus mobility with data from earlier studies regarding the common station. The research data has revealed i) sediment TP concentrations ranged from 620.00 mu gP gDW(-1), to 1047.50 mu gP gDW(-1) while TN concentrations were between 3250.00 mu g gDW(-1) and 6325.00 mu g gDW(-1). Sediment TOC concentrations ranged between 58850.00 mu g gDW(-1) and 79675.00 mu g gDW(-1). Sediment iron content and loss on ignition values were determined as 1.608-3.415 mg gDW-1 and 9.05-20.94 %, respectively. The rank order of phosphorus fractions were evaluated as Ca approximate to P>Org approximate to P>CO3 approximate to P>Fe+Al approximate to P. ii) the phosphorus release values from the sediment (0.1754 - 1.1249 mg P m(-2)d(-1)) were higher than the earlier studies findings. Phosphorus release in the lake has increased over the past ten years but still remains at a generally low level together with some management activities in Mogan Lake, therefore, instead of the internal P source future research should focus on external sources. In shallow eutrophic systems such as Mogan Lake, sediments having phosphorus accumulation depends on deep interactions with principally antropogenic external sources. In conclusion the primary goal is to determine the adsorption capacity of the sediment in order to estimate the critical internal phosphorus load and the second goal should be to apply a sustainable monitoring program.